1. Field of the Invention
The invention relates to a device for the low-deformation replaceable mounting of an optical element, in particular a closure plate of an objective of a projection exposure system for microlithography for the production of semiconductor components, in a mount of the type defined in more detail in the preamble of claim 1.
2. Description of the Related Art
A generic device is described in EP 1 107 034 A2. According to that, it is already known to provide the mount with at least three support feet distributed around the circumference on which feet the optical element lies and to introduce the adhesive layer in an annular gap between the mutually adjoining circumferential walls of mount and optical element, at least in some regions. The object of the previously known device is to mount the optical element at least largely free of deformation and avoiding stresses in the mount, in particular to achieve a mounting by means of which distortions changing over time can at least largely be eliminated. However, the mount described there can be set to the required lateral position only by means of an adjustment process and is accordingly not suitable for adjustment-free replacement. Because of the use of more than three fixing screws for holding the mount, the mounting of the mount that is described is subject to disadvantageous single-wave and multi-wave deformation which results from this.
Known holders and fixings of optical elements to mounts, in particular by means of adhesives, transmit forces and/or moments via the fixing to the optical elements. As a result of the adhesive connection of the optical elements, stresses can occur, which can lead to image defects of the respective optical element.
In the case of objectives in microlithography for the production of semiconductor components, from time to time subsequent corrections have to be provided in order to eliminate imaging defects or to increase the imaging accuracy. For this reason, individual optical elements, such as the closure plate, have to be designed to the replaceable in order that, for example, objective imaging defects can be optimized. The same is also true in the event of damage or wear of an optical element. This applies in particular to a closure plate in a projection objective. In the event of a replacement of this type, however, reproducibility should be achieved in order that new defects do not creep in.
For this purpose, it is already known from U.S. Pat. No. 5,973,863 to connect the closure plate of an objective in microlithography for the production of semiconductor components to the mount in a replaceable manner, in order that spherical aberrations or other image defects of the projection system can be corrected. To this end, a screw connection of the closure plate to the mount is proposed.